1. Field
The present invention generally relates to airborne spacing between an aircraft and a target aircraft.
2. Background
Several efforts have been undertaken to improve the efficiency of the National Airspace System (NAS). For example, Traffic Flow Management (TFM) concepts that better utilize NAS resources when controllers are managing traffic flows have been explored. Moreover, Time-Based Flow Management, which broadly describes the use of trajectory prediction on the ground to determine Estimated Times of Arrival (ETAs) and the ability of aircraft to more precisely fly their trajectories determined by the Flight Management System (FMS) to meet Scheduled Times of Arrival (STAs) throughout the NAS, has also been explored.
Improving the efficiency of operations in the terminal area has received particular attention. Reducing the variability of inter-aircraft spacing in the terminal area leads directly to increases in throughput. Decision support tools that aid the controller in sequencing, merging, and spacing aircraft—and the flight-deck avionics that support the flight crew in the same tasks—are thus being explored to provide this reduction while also reducing controller workload. The division of capability and responsibility for sequencing, merging, and spacing tasks between ground-based and flight-deck-based systems is important and has been the topic of studies in the past. Spacing accuracy has improved when controller tools are supplemented with aircraft equipped with avionics that aid in spacing.
Research into airborne spacing concepts, which use flight-deck avionics to manage the spacing relative to another aircraft, has been ongoing for several decades. EUROCONTROL and NASA Langley Research Center, for example, have evaluated airborne spacing concepts for terminal area spacing in fast-time simulation environments, human-in-the-loop studies, and field testing. Additionally, United Parcel Service has certified and field tested avionics for airborne spacing in their arrival operations at Louisville International Airport.
The concept of Interval Management (IM) has been developed by the Federal Aviation Administration (FAA) for near-term implementation supporting NextGen. IM provides precise timing within the airborne traffic flow by managing the relative spacing interval between a target aircraft (lead) and an IM (trail) aircraft, and thus increases the efficiency of a variety of air traffic operations.
The IM system includes an airborne component and a ground component. The airborne component of the IM system, namely the Flight-deck Interval Management (FIM), includes avionics onboard the IM aircraft, called the FIM equipment. The FIM equipment provides longitudinal speed guidance in an effort to achieve and/or maintain a desired spacing interval relative to a target aircraft assigned by the air traffic controller. A speed control algorithm in the FIM equipment determines the speeds of the IM aircraft as a function of IM and target aircraft states (e.g., horizontal position, vertical position, and horizontal velocity) and possibly other information about the environment. The IM aircraft is equipped with FIM equipment, and thus is capable of participating in IM operations. The ground component of IM, namely the Ground-based Interval Management (GIM), makes use of prediction tools on the ground, as well as the increased precision provided by FIM, to efficiently manage the spacing interval between aircraft within multiple environments and operations. In addition, GIM assists controllers in setting up the FIM operation by providing speed updates to meter aircraft to a point where the FIM operation begins. A facilitator of the IM concept is the expected widespread deployment of ADS-B Out and ADS-B In.
The precise spacing made possible by FIM, and managed by GIM, can facilitate IM operations with varying performance objectives, such as managing a schedule across sectors, enabling Optimized Profile Descents (OPDs), increasing throughput to a runway, and metering to a departure fix. An IM operation, as described herein, is an instance of an IM aircraft coupled to a target aircraft maintaining or achieving a desired spacing behind the target. For example, an IM operation can take place on departure, at arrival, or during en-route flight. IM operations are also referred to herein as “airborne spacing” operations.
IM operations are unified in concept and procedural design, but the scope of environments and operational contexts in which benefits are expected may result in functional performance characteristics that result in the needed performance and capabilities of the FIM equipment varying across the range of IM operations. Initial analysis of a set of near-term IM operations demonstrates that these performance differences exist.